I. Field of the Invention
The present invention relates to a package structure, and in particularly to a package structure with an overlaying metallic material over a solder material.
II. Description of the Prior Art
Generally, the solder material used in interior device of module package, such as QFN (Quad Flat No leads), QFP (Quad Flat Package), DIP (Dual In Line Package), BGA (Ball Grid Array) and LGA (Land Grid Array), mainly comprises Sn, such as SA, SAC and Sn—Zn. However, refer to FIG. 1A (Sn electrode 2, solder material: Sn 3, solder pad 4, PCB (printed circuit board) 5), solder material (Sn) 3 connecting interior device 1 to PCB (printed circuit board) 5 in module package is easily re-molten to cause two adjacent electrodes shorted by the Sn bridging 6 from one electrode to another in the second reflow process, and thereby a product failure will occur. In order to describe the Sn bridging 6 in detail, please refer to FIG. 1B. In the process of plastic-molding, the molding material 8 is usually EMC (epoxy molding compound), resin or other suitable material. However, it isn't effective to use molding material 8 to completely fill vacancy in the bottom of the device 1, and some voids 9 are then formed underneath the device 1. The solder material (Sn) 3 will enter into the voids 9 during the second reflow process, and then the Sn bridging 6 will occur.
Therefore, what is needed is a solution to resolve the Sn bridging issue inside a package structure during a reflow process in order to increase the product quality.